| Index: build/config/BUILDCONFIG.gn | 
| diff --git a/build/config/BUILDCONFIG.gn b/build/config/BUILDCONFIG.gn | 
| index d055e705627c96782434537d0157594ff4f6dad0..9cd7a7797b2776acdd46c7d6450946dd52e11769 100644 | 
| --- a/build/config/BUILDCONFIG.gn | 
| +++ b/build/config/BUILDCONFIG.gn | 
| @@ -135,8 +135,9 @@ declare_args() { | 
|  | 
| # Set to true when compiling with the Clang compiler. Typically this is used | 
| # to configure warnings. | 
| -  is_clang = current_os == "mac" || current_os == "ios" || | 
| -             current_os == "linux" || current_os == "chromeos" | 
| +  is_clang = | 
| +      current_os == "mac" || current_os == "ios" || current_os == "linux" || | 
| +      current_os == "chromeos" || current_os == "fuchsia" | 
|  | 
| # Allows the path to a custom target toolchain to be injected as a single | 
| # argument, and set as the default toolchain. | 
| @@ -161,7 +162,8 @@ declare_args() { | 
| # | 
| # For more information see | 
| # https://chromium.googlesource.com/chromium/src/+/master/docs/component_build.md | 
| -  is_component_build = is_debug && current_os != "ios" | 
| +  is_component_build = | 
| +      is_debug && current_os != "ios" && current_os != "fuchsia" | 
| } | 
|  | 
| assert(!(is_debug && is_official_build), "Can't do official debug builds") | 
| @@ -229,6 +231,8 @@ if (target_os == "android") { | 
| } else { | 
| _default_toolchain = "//build/toolchain/linux:$target_cpu" | 
| } | 
| +} else if (target_os == "fuchsia") { | 
| +  _default_toolchain = "//build/toolchain/fuchsia:$target_cpu" | 
| } else if (target_os == "ios") { | 
| _default_toolchain = "//build/toolchain/mac:ios_clang_$target_cpu" | 
| } else if (target_os == "mac") { | 
| @@ -279,6 +283,7 @@ if (current_os == "win" || current_os == "winrt_81" || | 
| current_os == "winrt_81_phone" || current_os == "winrt_10") { | 
| is_android = false | 
| is_chromeos = false | 
| +  is_fuchsia = false | 
| is_ios = false | 
| is_linux = false | 
| is_mac = false | 
| @@ -288,6 +293,7 @@ if (current_os == "win" || current_os == "winrt_81" || | 
| } else if (current_os == "mac") { | 
| is_android = false | 
| is_chromeos = false | 
| +  is_fuchsia = false | 
| is_ios = false | 
| is_linux = false | 
| is_mac = true | 
| @@ -297,6 +303,7 @@ if (current_os == "win" || current_os == "winrt_81" || | 
| } else if (current_os == "android") { | 
| is_android = true | 
| is_chromeos = false | 
| +  is_fuchsia = false | 
| is_ios = false | 
| is_linux = false | 
| is_mac = false | 
| @@ -306,6 +313,7 @@ if (current_os == "win" || current_os == "winrt_81" || | 
| } else if (current_os == "chromeos") { | 
| is_android = false | 
| is_chromeos = true | 
| +  is_fuchsia = false | 
| is_ios = false | 
| is_linux = true | 
| is_mac = false | 
| @@ -318,15 +326,27 @@ if (current_os == "win" || current_os == "winrt_81" || | 
| # Posix variant. | 
| is_android = false | 
| is_chromeos = false | 
| +  is_fuchsia = false | 
| is_ios = false | 
| is_linux = false | 
| is_mac = false | 
| is_nacl = true | 
| is_posix = true | 
| is_win = false | 
| +} else if (current_os == "fuchsia") { | 
| +  is_android = false | 
| +  is_chromeos = false | 
| +  is_fuchsia = true | 
| +  is_ios = false | 
| +  is_linux = false | 
| +  is_mac = false | 
| +  is_nacl = false | 
| +  is_posix = true | 
| +  is_win = false | 
| } else if (current_os == "ios") { | 
| is_android = false | 
| is_chromeos = false | 
| +  is_fuchsia = false | 
| is_ios = true | 
| is_linux = false | 
| is_mac = false | 
| @@ -336,6 +356,7 @@ if (current_os == "win" || current_os == "winrt_81" || | 
| } else if (current_os == "linux") { | 
| is_android = false | 
| is_chromeos = false | 
| +  is_fuchsia = false | 
| is_ios = false | 
| is_linux = true | 
| is_mac = false | 
|  |